1. Field of the Invention
The present invention relates to techniques for control of a read-out state of data on automatic performance.
2. Description of the Related Art
An automatic performance apparatus sequentially reads out data on automatic performance stored in a memory, and delivers this data to a sound source circuit to thereby reproduce a musical tone automatically.
In this case, the reproduction tempo of the automatic performance is generally determined by a fixed tempo clock. General techniques for changing the reproduction tempo use an up switch and a down switch such as those disclosed in published unexamined Japanese patent application Hei 2-244094 (published Sep. 28, 1990). The user operates the up switch and down switch to change the frequency of the tempo clock and hence the reproduction tempo. However, depression of a switch such as that technique is not easy for the user to use because the user must depress the switches many times/continue to depress them to gradually change the frequency of the tempo clock in order to arrive at a desired reproduction tempo.
A "disk jockey" who is in charge of control of record reproduction in a "discotic" manner uses an operating method "scratch" such as changes the rotational speed of the record disk by depressing the rotating record disk with his fingers to change the reproduction tone of the record.
When such operation technique "scratch" is applied to the automatic performance apparatus, the use of the up switch/down switch would not achieve a very rapid tempo adjustment.
CASIO Computer Co., Ltd. to which this invention is expected to be assigned has manufactured and sold since Jun. 20, 1991 articles which produce a sound in accordance with the rotation of a "scratch disk" attached to an electronic musical instrument under the trade name "RAP-1 ".
This article has a first and a second switch below the scratch disk. By rotating the scratch disk clockwise through a predetermined angle to render the first switch conductive while it is rotated counterclockwise through a predetermined angle to render the second switch conductive. When the first and second switches are rendered conductive, sounds with different timbre scratch effects are produced. As just described above, the scratch disk of the conventional electronic musical instrument only rotates the rotating disk through a predetermined angle to produce a special effect sound in place of depression of a push button.
Therefore, even if the scratch disk techniques for the conventional electronic musical instruments are applied to an automatic performance apparatus, the device still has the same drawbacks as the conventional up switch/down switch. Thus, the development of a scratch disk suitable for automatic performance has been desired.